Monday, April 2, 2012

“There is Nothing Paranormal About Near-Death Experiences: How Neuroscience Can Explain Seeing Bright Lights, Meeting the Dead, or Being Convinced You Are One of Them”

Authors: Dean Mobbs and Caroline Watt

Journal: Trends in Cognitive Science

Volume 15, number 10 October 2011

The Exterior:

A review of neurosciences which demonstrates the scientific evidence that experiences of the afterlife are nothing more than side effects of normal neurological happenings. To put it bluntly, near-death experiences really are all in the mind. This paper is a really tidy review of what science has to say about the experience of death and that really, there is nothing metaphysical going on.

The Guts:

The paper is a review of current research in neuroscience, which reveals the evidence that near death experiences are not paranormal. Approximately 3% of the American population declare experiencing such experiences, and I guess, will be disappointed it is not Grandma May or Aunt Tilda reaching out to them, but simply artefacts of their neurology. To begin, a short list of common features was provided, followed by the current scientific explanation for each. Here they are:

1. An Awareness of Being Dead: Out of body experiences are not limited to near death experiences. However, this sensation can be put down to “Cotard” or “Walking Corpse” Syndrome. It is thought that this syndrome is associated with the parietal cortex and prefrontal cortex, and has been documented during the advance stages of typhoid, multiple sclerosis and following trauma. The syndrome can include delusions, and while a scientific explanation as to why such delusions occur is unknown, the authors suggest it may be an attempt by the individual suffering the syndrome to make sense of a strange experience.

That bright light is nothing more than tunnel vision....

2. Out of Body Experiences: Again, this is not one confined to near death experiences. A neurosurgeon by the name of Wilder Penfield argued such experiences were based in the brain. Interestingly, the review points out that these experiences often occur when REM sleep is interrupted, resulting in paralysis but with an awareness of the external world. The reviewers discussed a study where it was shown that out of body experiences could be artificially created by stimulating the right temporoparietal junction of the brain. The conclusion drawn was that out-of-body experiences may result from a failure to integrate multisensory information and thus disrupt elements of self-representation.

3. Seeing a Tunnel of Light: The experience of moving toward a bright light is synonymous with being drawn from the living to the dead. However the experience is sometimes documented by pilots flying at G-Force, a condition that is known as hypotensive syncope. The effect of the G-force causes tunnel-like vision due to a loss of vision. The case of near-death of experiences is not as well explained, however, it is thought that the light at the end of the tunnel is a result of oxygen supply to the eye being depleted (otherwise known as retinal ischemia). Such tunnel vision has also been associated with fear and oxygen loss (hypoxia), both conditions associated with dying.

4. Meeting Deceased People: Encountering the dead is an experience favoured by writers across the ages, usually to convert a less than savoury character to living a moral life because they were warned from a dead relative on the other side to pull their act together. Another commonly used plot device, is someone dying and being surrounded by angels as one departs this life, to be carried toward the bright light (that part we already have a good explanation for). Those visions of encountering long-dead Aunty Martha, are most likely hallucinations, which are thought to be caused by compensatory mechanisms in the brain. This compensation leads to over-activation in brain structures due to stress or damage (most likely due to lack of oxygen as organs shutdown) leading to said hallucinations. Interestingly the authors point out that similar hallucinations can be caused by lesions on the brain, macular degeneration and as a side effect ofdiseases such as Alzheimer’s. People with all of these disorders recount vividly seeing everything from dead relatives to fairy-tale characters. Once again, this effect can be replicated during experiments by stimulating certain areas of the brain with electricity ; the result being patients reporting the presence of someone standing behind them.

5. Positive Emotions: When faced with dying, people often get scared. However upon encountering the bright light, the angels and realising is life is slipping between your fingers, many report feeling calm, even euphoric – the fear simply evaporates and is replaced by positive emotions. A compound called ketamine can be used medicinally to mimic such feelings, and at different doses can result in hallucinations, out of body experiences and the aforementioned positive emotions. It is thought that similar neurochemical compounds are released. These pathways include mechanisms leading to opioid and dopamine release, and are thought to occur as a result of disruption of the prefrontal cortex during the process of death. A similar effect is seen in animals when under predatory attack, an example that demonstrates that similar pathways are triggered in highly traumatic events (death could be certainly be considered traumatic!).

The Skeleton:

The bare bones of the paper (excuse the pun) come down to this: despite the fact that the underlying mechanisms for all the phenomena of near death experiences are not yet clear, the scientific evidence suggests that all aspects of near death experience have a neurological or psychological basis. The expectations of an individual who is expecting the whole ‘near death package’ may also play a role in what is experienced, if you expect to see your long dead relatives or angels, then there is a higher likelihood your brain will manifest such things.

At the end of the day, there isn’t any paranormal activity going on when it comes to dying. The angels you see are hallucinations, the bright light is a result of oxygen deprivation and the sensation of one’s life flashing in front of one’s eyes is due to neurotransmitters. Near–death experiences are essentially the experienced effects of normal brain processes gone awry during the traumatic event of a body nearing death. That being said, uncovering the way the mind produces these phenomena is nothing short of fascinating. Future research will hopefully uncover some of the actual reasons that underpin the experience of dying, for it certainly isn’t anything to do with angels or long dead relatives.

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I like long walks on the beach and dissecting your genetic code. Scientist who does lots of genomics to pay the bills but also fascinated by neuroscience, citizen science and astronomy. Often bakes, knits and enjoys whisky, books and music.
A blog on genomics, biology, medicine and the experiences of a scientist, as well as exploration of the intersection of science and society.
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